Packing for pistons of rock-drills



(NoModeL) H. M. OSBORN.

PACKING FOR PISTONS OF ROCK DRILLS.

No. 520,448. Patented May 29, 1894.

Vii/55a;

UNrTE HEMAN M. OSBORN, OF CALUMET, MICHIGAN.

PACKING FOR PISTONS OF ROCK-DRILLS.

SPECIFICATION forming part of Letters Patent No. 520,448, dated May 29,1894.

Application filed July 15, 1893- Serial No. 480,608. (No model.)

To all whom it may concern.-

3e it known that I, HEMAN M. OSBORN, a citizen of the United States,residing at Calumet, n the county of Houghton and State of Mlchigan,have invented certain new and useful Improvements in Packings for thePistons of Rock Drills, of which the following is a full, clear, andexact description, reference being had to the accompanying drawings,forming a part of this specification.

My invention relates to the packings of the pistons of rock-drillsgenerally, and more par- 'ticularly to the piston packings of suchrockdrills as are designed to utilize compressed air as their motive oractuating medium; my invention being nevertheless equally applicable torock-drills using steam or other fluid under pressure as their actuatingor motive medium.

Among the primary objects of my invention is included that of producinga packing which shall avoid all cutting of the drill-cylinders, and alsoall consequent pounding of the pistons against the backs of thecylinders, such as interferes with the proper manipulation of thefeed-screw cranks of the drills. A further primary object of theinvention is to produce a packing which shall be free from all liabilityto fracture, and thus avoid the frequent disablement of the drills dueto such fracture. Also to produce a packing which shall render the useof expansion-springs for the packing unnecessary and which shallconsequently avoid the present frequent disablement of the drills frombreakage of such springs. Still further, to produce a packing whichshall neutralize any injurious effects of breakage of certain adjacentparts of the drill; which shall absorb lubricants and thus assist in thelubricating action upon the parts, and which finally shall avoid thewiping away of the lubricant and the consequent disablement of thedrills due to the sticking of the pistons in the cylinders.

To the above purposes as also to such others as may appear from theensuing description my invention consists in certain peculiar and novelfeatures of construction and arrange-- ment, as hereinafter describedand claimed.

The more precise nature of my invention will bebetter understood whendescribed with reference to the accompanying drawings, in which Figure lis a central longitudinal section of a part of a rock-drill having itspistons provided with a packing embodying my inven- .tion. Fig. 2 is anend-elevation of a packing embodying my invention; the said packingbeing in detached condition. Fig. 3 is a side elevation of the packing.Fig. 4 is an endelevation of the rotating nut.

Before giving a detailed description of the structure shown in thedrawings as embodying my invention, I will state, as clearly and brieflyas possible, the principal defects which are found in the spring-pressedsectional metal piston packings heretofore commonly used in suchrock-drills as the Ingersoll and Sargeant drills, the Rand and Bullockdrills, and similar rock-drills now in most general use. These drillsare all provided with packings, for their pistonbars, consisting ofsteel sections pressed outwardly by spring-action. When these drills arenew, or when their packings are in even the most perfect condition, theyare seriously defective, because since the contacting surfaces of thecylinders and the metal packing ring sections are necessarily made assmooth as possible, the moisture, which is always present in compressedair, Works through between these smooth contacting surfaces and thuscauses the lubricating oil to be wiped off by the moving metal packing.The result is that the piston-bars stick so firmly in the cylinders thatthe miners cannot dislodge them and they have to be sent back to theshops for repairs. Furthermore, at the commencement ofdrilling-operations, the surface upon which the drilling-bits strike areusually uneven (the miners not taking time to first level off suchsurfaces) and the consequence is that the piston-bars are subjected toviolent lateral shocks or strains which cause the" metalpacking-sections to cut into the smooth surfaces of the cylinders andthus rapidly wear the bores of the cylinders out of true; this c'uttingaction usually causing the cylinders to assume internally a barrel-format one or more points and the resulting leakage of air or steam aroundthe packings, lessening the effective power of the drills and soontotally disabling them. It is a fact that an enlargement of only threeor four-one-thousandths of an inch is sufficient to seriously impair theeffectiveness of a drill, and hence the importance of this defectiveaction is apparent. As a further consequence of this lateral wearing ofthe cylinder-bores, the necessary cushioning of the piston-bars on theback-stroke is prevented (owing to the leakage around the packings) andthe piston-bars consequently pound so violently against the backs of thecylinders that it is impossible for the operators to retain a steadygrasp upon the feed-screw cranks.

The previous forms of piston-bar packings are still further seriouslyobjectionable, inasmuch as the metal-ring sections and also theirsprings are exceedingly liable to become fractured under the violentaction of the drills, and the broken fragments resulting from suchfractures speedily cut or score the interior walls of the cylinders,rendering the machine useless by reason of the resulting leakage aroundthe piston-bars. This objection also 2 5 applies to the internalshoulders at the backs of the cylinders, which are also liable tofracture from the described pounding of the piston-bars, on theirback-strokes, and the fragments of which similarly cut or score thecyl-' o inder-walls. 1

I have thus explained in detail the defects of the metal-packing-ringsheretofore used, because such defects are, each and all, entirelyavoided by my invention. I do not use metal packing at all, nor do I usemetal or any other springs. I use a packing which is so soft and pliablethat it cannot possibly cut or wear the cylinder walls, and whichutilizes the expansive force of the actuating o fluid to eifect itsexpansion, and which, furthermore, permits any fragments from theinternal shoulder (in the Very remote contingency of fracture of suchshoulder) to so embed themselves in the packing that they can- 4 5 notcut or score the cylinder-walls.

Referring now to the drawings, in which I have shown my invention asapplied to a Sargeant rock-drill, 1 designates thecylinder of the drill,2 the valve-chest and 3 the valve thereof.

4 designates the feed-screw, 5 the feedscrew crank, 6 the shell in whichthe drillcylinder slides.

8 designates the goose-neck, shown as bolted 5 5 at 9 to the shell 6 andas forming, at its rear end, a bearing for the feed-screw crank 5.

1O designates the piston-bar having at its outer end a suitable socket(not shown) for the bit and at its inner end formed with or properlyconnected to a piston 12.

13 designates the rifle-bar which extends into a longitudinal bore inthe piston 12 and which at its rear end carries the rotating ratchet 14:acted upon by the usual rotating pawls (not shown).

A more detailed description of the drill is not deemed necessary herein,since such parts may be either of the precise form and arrangement hereshown, or of any other form and arrangement usual with the class ofdrills of which that illustrated forms a type.

The rear end of the piston 12 is internally screw-threaded, as at 15,and is also externally somewhat enlarged as at 16; the internalscrew-threadin g of this enlarged portion 16 being for the purpose ofadmitting the rotatingor packing-nut 17. This packing-nut (orrotating-nut, as it is usually called) is externally screw-threaded toengage the internal screw-threads 15 of the piston 12, and is formedwith an internal longitudinal bore 18 extending throughout the entirelength of the nut and having the usual lateral spiral grooves 19 toreceive the external spiral ribs of the rifle-bar 13'. This packing-nut17 is formed at its rear end with an external circular enlargement 20the front edge of which is perfectly rounded off as shown at 21.

22 designates the flexible packing, this packing having a centralopening 23 the margin of which closely surrounds the body-portion of thenut 17 adjacent to the front end of the enlargement 20, so that saidpacking lies closely against said end of the enlargement. The width ofthe packing 22, from its outer margin to the margin of its opening 23,is such that, when, the packing is in proper position, the outer marginor edge of the packing shall protrude outward and backward between theouter surface of the enlargement 20 and the sides of ,the cylinderbore;the external diameter of the enlargement 20 of the nut being just somuch less than the external diameter of the enlargement 16 of the pistonso as to aiford room between the outer surface of the enlargement 20 andthe cylinder-wall, for the outwardly and backwardly protruding portionof the packing 22. This packing 22 is preferably of leather, as suchmaterial best fulfills all of the various working requirements of thepacking, but it may be of any suitable soft and flexible and at the sametime durable material. Owing to its softness, the packing cannotpossibly cut or score the walls of the cylinder and it is sufficientlyabsorbent to take up moisture from the compressed air and also part ofthe oil used for lubricating the piston. Hence the packing assists inlubricating the piston, since, during each stroke of the piston, thepacking applies some of its absorbed lubricant to the walls of thecylinder. Owing to the outward and backward extension of the packing,the compressed air expands the packing against the cylinderwalls, duringeach forward stroke of the piston, so that there can be no leakage ofair around the packing. The only parts which could possibly becomefractured are the rotary back washer 24 and the shoulder 25 within thecylinder, and in the improbable event of such fracture the softness ofthe packing enables the fragments to embed themselves into the packingwithout cutting or scoring the cylinder-Walls. It is also to be observedthat it is impossible for the flexible packing to work out of its properposition, because the torsional action of the rifle-bar upon thepacking-nut serves to constantly tighten the nut against the packing.

Having thus described my invention, what I claim as new therein, anddesire to secure by Letters Patent, is-

1. The combination with the piston of a rock-drill, a rotatingpacking-nut having screw-threaded connection with said piston, and arifle-bar working through said packing-nut, of a flexible and absorbentnon-me tallic, packing surrounding the nut and interposed between saidnut and the piston, and also protruding outwardly and rearwardly aroundthe nut, substantially as set forth.

2. The combination with the piston of a 20 H. M. osBoRN.

Witnesses:

JAMES SowDEN, JERRY L. SULLIVAN.

